1. Field of the Invention
The present invention relates to an apparatus which obtains information on a given curved tomographic orbit as two-dimensional panoramic images. This apparatus can be used as a panoramic radiographic apparatus for dental treatment which photographs human dental arches. The apparatus can also be used as a tomographic apparatus which photographs human regions other than dental arches or as a tomographic apparatus for nondestructive inspection of various substances.
2. Description of the Prior Art
As this kind of apparatus, a dental panoramic radiographic apparatus which uses films is well known. The apparatus has an X-ray source disposed opposite to a film with the dental arch of a patient positioned therebetween and relatively moves the X-ray source and the film in a predetermined ratio between the rotation speed of the X-ray source and the movement speed of the film to form an X-ray image of the dental arch a panoramic image on the film by using the X-ray which penetrated the dental arch. This kind of apparatus has various problems caused by photographic technology which uses films. To solve these problems as a primary object, the applicants of the present invention have already proposed an apparatus which obtains desired panoramic images by electrically processing X-ray penetration images without using films (for example, Japanese Patent Publication No. 2-29329).
However, the conventional radiographic method has a narrow tomographic area, making it difficult to position the patient properly. In addition, when obtaining a given tomographic image layer, it is also difficult to set the proper relative positional relationship between the film and the tomographic image layer. Furthermore, the panoramic image of only one preset tomographic image layer can be obtained by a single photographing operation and information other than the panoramic image of the preset tomographic image layer is discarded. If the image of a different tomographic image layer becomes necessary, another photographing operation is required. This increases the number of photographing operations, causing much trouble. This also increases the amount of X-ray radiation exposure dose, causing a problem when a human body, such as a dental arch, is photographed. This problem is also caused when a panoramic image is obtained by the electric processing.
Moreover, the image of an object located other than the target tomographic image layer is superimposed on the panoramic image obtained by this kind of apparatus as a blurred image. This ghost image cannot be eliminated by the conventional method.